1. Field of the Invention
The present invention is directed to a composition containing a compound produced by the reaction of glycine, an alkyl substituted glycinate or salts of these compounds with formaldehyde which effectively inhibits microbial growth in a variety of substances.
2. Description of the Prior Art
Reports on the reaction of glycine with formaldehyde is limited to work done over 50 years ago. W. Lob [Biochem. Z., 51, pp. 116-127 (1913)] reported that glycine (also called aminoacetic acid and glycocoll) plus formaldehyde formed the Schiff base in neutral solution and formed methylenediglycine, isolated as the dihydrochloride, in acid solution. Lob did not report isolating a product from reaction in alkaline solution. Following Lob, H. Krause [Ber., 52, pp. 1211-1222 (1919)] described the preparation of sodium or potassium salts of hydroxymethylglycine by low temperature reaction in aqueous solution. Krause also described the preparation of other salts, e.g., barium, lead, silver, copper, mercury and calcium salts, of hydroxymethylglycine from either glycine salt plus formaldehyde or by replacement of the sodium or potassium cation of the hydroxymethylglycine salt.
More recently, N-hydroxymethylglycine is disclosed in U.S. Pat. No. 3,291,606. In that patent, a photographic color image is reported to be protected against fading and discoloration caused by intense tungsten illumination when bathed in an aqueous solution of glycine, glycylglycine or N-hydroxymethylglycine. The source of the N-hydroxymethylglycine is not disclosed.
Recent survey articles discussing the reaction between glycine and formaldehyde have stressed the complexity of the chemistry. See, e.g., Rodd, The Chemistry of Carbon Compounds, 2nd Ed. Vol ID (1965) p. 167. For example, while the condensation of the sodium salt of glycine with formaldehyde may be viewed as a simple addition reaction: ##STR1## it can also be much more complicated because the hydroxymethyl derivative could dehydrate to a Schiff base, react with another molecule of glycine or polymerize. Thus, rather than term the reaction product simply sodium hydroxymethylaminoacetate, it is more accurate to speak of it as an equilibrium mixture of compounds produced by the reaction of the sodium salt of glycine with formaldehyde. The precise proportions of the particular compounds in the mixture will depend on the particular reaction conditions.
While it is evident that the prior art has long recognized that salts of glycine could be reacted with formaldehyde, there is little disclosure regarding the utility of the reaction product.